using System; class Employee: IFormattable { public Employee(int id, string firstName, string lastName) { this.id = id; this.firstName = firstName; this.lastName = lastName; } public string ToString (string format, IFormatProvider fp) { if ((format != null) && (format.Equals("F"))) return(String.Format("{0}: {1}, {2}", id, lastName, firstName)); else return(id.ToString(format, fp)); } int id; string firstName; string lastName; } public class CustomObjectFormatting { public static void Main() { Employee fred = new Employee(123, "AAA", "BBB"); Console.WriteLine("No format: {0}", fred); Console.WriteLine("Full format: {0:F}", fred); } }